Q2 semiconductor sales down 20% vs year ago: SIA LONDON (MarketWatch) -- Worldwide sales of semiconductors for the second quarter of 2009 were $51.7 billion, the Semiconductor Industry Association said Monday. Sales declined by 20% compared to the same period a year ago but rose 17% from the first quarter. Worldwide sales in June were $17.2 billion, up 3.7% from May but down 20% from the same month last year.